November 18, 2012

Lonesome George’s Species May Not Be Extinct After All

At the time of his death, it appeared that Lonesome George was the last member of his species, but new research suggests that his breed of giant tortoises might live on after all.

According to Jennifer Viegas of Discovery News, experts at Yale University have reportedly discovered DNA evidence suggesting that members of the species Chelonoidis abingdoni could still exist.

Those researchers collected genetic material from more than 1,600 giant tortoises, and discovered 17 hybrids that were ancestors of Lonesome George -- and some of them could have been sired by purebred C. abingdoni tortoises, Viegas added. Their findings have been published in the journal Biological Conservation.

The Yale researchers conducted genetic testing at an area known as Volcano Wolf on the island of Isabela, one of the Galapagos Islands (traditional home of the C. Abingdon), explained Sasha Ingber of National Geographic News. There, they managed to identify three male turtles, nine female turtles, and five juvenile turtles (less than 20 years of age) that share DNA with Lonesome George's subspecies.

The presence of juvenile tortoises give the authors hope that they will be able to help resurrect the species.

“Our goal is to go back this spring to look for surviving individuals of this species and to collect hybrids,” Adalgisa 'Gisella' Caccone, senior author of the study and a research scientist at the university's Department of Ecology and Evolutionary Biology, told Viegas. "We hope that with a selective breeding program, we can reintroduce this tortoise species to its native home."

"This isn't the first time Chelonoidis nigra abingdoni has been revived: The massive reptiles were last seen in 1906 and considered extinct until the 1972 discovery of Lonesome George, then around 60 years old, on Pinta Island," added Ingber. "The population had been wiped out by human settlers, who overharvested the tortoises for meat and introduced goats and pigs that destroyed the tortoises' habitat and much of the island's vegetation."

According to Warwicker, female members of the species tend to mate with multiple male partners, and are capable of storing sperm within their bodies for multiple years. The researchers determined that when siblings sired by multiple fathers were hatched, the mating order of those fathers did not impact the chances of a successful fertilization.

While prior research had suggested that the last male to participate in the mating process would have been responsible for the majority of the offspring, Dr. Sara Fratini and her colleagues found evidence suggesting that the sperm tended to become mixed in the oviduct of the female Hermann's tortoises, BBC Nature reported.

"Sperm storage has been frequently reported in reptiles and birds, and is associated with a promiscuous mating system," Warwicker said. "Chelonian species are known for their long-term sperm storage, and females are capable of storing viable sperm for three or four years in specialized tubes within their oviduct."

"To better understand this system the team set up a series of planned matings between Hermann's tortoises (Testudo hermanni hermanni) and conducted paternity tests on tortoise hatchlings from 16 egg clutches," she added. "They found that 46% of the clutches had been 'multi-sired': fertilized by two or three males."

Furthermore, they determined that of the egg clutches that had been fertilized by at least three different male tortoises, a "significant" amount of genetic material from previous partners had been found in the distribution of the sperm, Warwicker said. Dr. Frantini also believes that female tortoises might also intentionally use older sperm before the newer sperm, in order to make sure that it is still effective.

Fratini, along with Giulia Cutuli, Dr. Stefano Cannicci and Professor Marco Vannini, detail their findings in the latest edition of the journal Behavioral Ecology and Sociobiology.